Give a pinned item the pinned feed's disc (#121)

A pinned feed has a disc in the theme's accent, its pin in the ink the theme pairs with it;
a pinned item only turned its pin solid in the text colour. The item's pin button now draws
the same disc, as a background inside its 22px button so the row does not move when an
item is pinned. The colours are the ones .fpin already uses; no palette changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - The Directory browses as Apple's does: a row of categories, and once one is picked, a row of its subcategories (Tech News under News, Video Games under Leisure), instead of one row mixing both.
+- A pinned item in a list wears the same disc as a pinned feed, in the theme's accent, instead of a plain solid pin.
 - An item published without a title shows its opening words, in plain text rather than bold, instead of "(untitled)"; one with no text either shows its file's name, or its show and date. Opened, it starts with its text.
 - A feed that has moved for good (a permanent redirect) is followed to its new address, which iPX then reads from, and says so in the log as `feed_moved`. A temporary redirect changes nothing.
 - The daemon sleeps until the next feed is due, at most ten minutes, instead of looking every minute; refreshing or adding a feed still wakes it at once.